LEPTAUCHENIA 237 



assume the shape of the wide, transversely flattened lumbar spines. A few proximal caudals are preserved, too 

 few to determine with certainty whether the tail was long or short, but suggesting the latter from their com- 

 paratively small size. In the cervical series, the atlas is characterized by a slender inferior arch and broad superior 

 arch with strong backward slope to its dorsal profile. The canal for the vertebral artery perforates the base of the 

 transverse process at the margin of the posterior cotylar surface, where it is inclosed by but a narrow bridge of 

 bone, soon emerging on the lower surface of the process. Some distance anterior to the point of emergence, it 

 again perforates the transverse process, joining the neuro-arterial canal near its point of emergence. The margin 

 of the transverse process is broken in all the specimens examined, but seems to have been circular. The axis 

 carries a large neural spine, of which the dorsal border slopes strongly backward and upward. All the transverse 

 processes of the cervicals are perforated by the vertebral artery. 



The scapula is a triangular element of which the outer surface is divided unequally into large post- and 

 small pre-spinous fossa; by the prominent scapular spine, of which the acromion process is directed forward. Of 

 the pelvic girdle, the ilium is broadly expanded in the transverse plane, rather more so than the figure would indi- 

 cate. The gluteal fossa is shallow and the anterior superior spine quite prominent. The ilio-pectineal eminence 

 varies in prominence in different specimens. Both ischial and pubic rami are stout. . . . 



The strong forward curvature of the radius and heavy olecranon process of the ulna are perhaps the most 

 striking features of the forelimb. Apart from this, there are no peculiarities which call for special comment. . . . 

 But one terminal phalanx is represented in the Princeton collection, and of this the tip is broken off and the 

 margins somewhat damaged. It seems to have been a small pointed hoof. 



The humerus is proportionally Jong and slender, with the distal end decidedly broad. 



Discussion: A skull, with jaws attached, was collected in 1914 by John T. Doneghy, Jr., at 

 Rattlesnake Butte, about six miles southwest of Chadron, Nebraska. This skull is that of an 

 immature individual, in which neither superior nor inferior third molar is erupted and the milk pre- 

 molars are still present. It was found in the lower Miocene beds and is probably a male. 



This specimen, Cat. No. 12221 Y.P.M., is fairly well preserved, with the exception of the 

 superior part of the muzzle in advance of the orbits, including the superior incisor border. The 

 chief characters may be briefly set forth. The total length of the skull is approximately that of 

 L. decora, but in the fully adult form it must have been somewhat longer. The sagittal crest is 

 short and has a nearly straight contour. From the junction of the temporal ridges, the upper contour 

 descends steeply to the tip of the nasals, giving an anthropoid appearance from a lateral view. The 

 orbits are small and look chiefly upward and outward, in which respect it is more like L. major, 

 although this feature is more pronounced than in the latter species. The bregma, the junction of 

 the sagittal and coronal sutures, is situated considerably farther in advance of the junction of the 

 temporal ridges than in L. decora and holds more nearly the position seen in L. nitlda. In L. major 

 the bregma is located at the junction of the temporal ridges. The malar below the orbit is more 

 robust and deeper in this submature specimen than in an average fully adult L. decora. The infra- 

 orbital foramen is above the interval between P 2 and P 3 . The bulla? are of different shape than in 

 any other species of the genus, but whether or not this is an adolescent feature I have no way of 

 determining at present. In outline, they are roughly circular and much inflated. They are propor- 

 tionally as large as in L. nitlda and absolutely larger than in L. decora. They are farther apart, 

 however, than in L. nitlda, and their internal faces do not parallel each other vertically, as in the 

 latter species. The paramastoids are broad above and extend downward and considerably outward 

 below the inferior edge of the bullae, with which they are in contact for a part of their course. I 

 fail to find this outward direction in the adult Yale specimens of the three species, in all of which they 

 extend almost directly downward. 



The ramus is decidedly robust for a submature animal. The inferior border is very gently 

 curved, as in L. decora, and does not turn downward at the angle, as in L. major. The coronoid 

 process extends but slightly above the condyle, more as in L. major, and its superior edge does not 

 curve backward so much as in L. decora. The masseteric fossa is unusually deep, and the ramus is 

 very robust below the molar series. With respect to the occipital condyles, the external auditory 

 meatus is situated much farther back than in L. nitlda but approximately the same as in L. major and 

 L. decora, although relatively somewhat higher. 



